In recent years, integrated optical devices have received tremendous attention as they provide low cost, high density and high data rate devices for a wide range of applications. Integrated optical devices have also been increasingly used for sensing applications because of their inherent characteristics such as high sensitivity, miniaturisation, mechanical stability and immunity to electromagnetic interference.
Optical device fabrication processes, which adopt planar CMOS technology from the mature microelectronics industry, offer ease of manufacturing and the possibility of simultaneous detection of several analytes on a single chip. Various methods have been implemented for the design of integrated optical biosensors, such as waveguide surface plasmon resonance, waveguide grating coupler, Mach-Zehnder and nanocavity.
For biosensing applications, a number of sensor configurations have been proposed, including Mach-Zehnder interferometer (MZI) and microcavity sensors.
However, most existing proposals are limited to single sensing channels. A multiple sensor device with multiple sensing channels based on such proposals typically requires one light source for each sensing channel.
In realising multiple sensing channel devices using only a single source, existing optical combiner/splitter structures have a number of disadvantages. For example, in one configuration, arrays of interconnected 3-dB couplers may be used to realise n×N couplers. Such a configuration suffers from disadvantages such as high optical losses and an accumulative size of the overall device.
Alternatively, interference based integrated n×N star couplers have been proposed. However, such couplers suffer from high optical losses and complexity of manufacturing.
A need therefore exists to provide an optical combiner/splitter structure that seeks to address at least one of the above disadvantages.
On the other hand, a need also exists to provide an active optical component for use in optical devices such as sensors or communication devices, the active optical component having improved performance in terms of at least one of attenuation and/or driving power.